Inducing desirable temperature effects on body tissue

Abstract

Methods and systems are disclosed for treating diseased tissue by gentle heating. The method induces vasodilation on tissue disposed about an lumen having both healthy tissue and diseased tissue. The method includes coupling a probe surface to the luminal tissue at a target location and transmitting desired quantities of tissue remodeling energy from the coupled probe into each of a plurality of discrete remodeling zones in the luminal tissue so that the tissue remodeling energy heats the plurality of remodeling zones, the remodeling energy being configured to avoid muscular contraction and inhibit both acute and long-term occlusion of the lumen.

What is claimed is: 
     
       1. A method of treating a target tissue within a treatment area disposed about a body lumen, comprising:
 providing a catheter having a catheter body and an energy delivery portion mounted on the catheter body, wherein the energy delivery portion comprises a balloon having a plurality of electrodes spaced apart about a circumference of the balloon, the plurality of electrodes including a first electrode, a second electrode, a third electrode, and a fourth electrode; 
 inserting the energy delivery portion of the catheter into the body lumen, positioning the energy delivery portion adjacent the treatment area, and expanding the balloon so that the plurality of electrodes radially engage the body lumen and contact between the plurality of electrodes and the body lumen defines a plurality of energy delivery zones within the treatment area, wherein the treatment area includes the target tissue and a healthy tissue; 
 delivering energy to the body lumen at the plurality of energy delivery zones, each of which is small compared to the treatment area so that the plurality of energy delivery zones are separated about the balloon, wherein the delivering energy comprises energizing the first, second, third, and fourth electrodes, wherein the plurality of electrodes comprise a plurality of electrode pairs, wherein the delivering energy further comprises energizing selected electrode pairs of said plurality of electrode pairs with a bipolar energy, wherein the bipolar energy is delivered from the selected electrode pairs according to a formula as follows:
   power= b *x^2* L *( t ^(−0.59))
 
 
 
       where b ranges between 0.2 and 0.6, x is an inner edge-to-edge spacing between the electrodes of the selected electrode pairs in millimeters, L is a length of the electrodes of the selected electrode pairs in millimeters, power is in Watts, and t is time of the bipolar energy delivery in seconds, wherein energizing a first electrode pair of the selected electrode pairs comprising the first and second electrodes heats the healthy tissue without therapeutically heating the target tissue and energizing a second electrode pair of the selected electrode pairs comprising the third and fourth electrodes heats the target tissue sufficiently to efficaciously alter the target tissue without causing sufficient thermal damage to the healthy tissue to induce a long-term occlusive response, and wherein the first, second, third, and fourth electrodes are energized without identifying which of the plurality of electrodes heats the target tissue. 
     
     
       2. The method of  claim 1 , wherein the delivering energy heats the healthy tissue to a maximum healthy tissue temperature and heats the target tissue to a maximum target tissue temperature, and wherein the maximum healthy tissue temperature is significantly lower than the maximum target tissue temperature. 
     
     
       3. The method of  claim 1 , wherein the delivering energy comprises introducing into the treatment area entirely through the healthy tissue, wherein all of the plurality of electrodes are in contact with the healthy tissue so that heat is generated volumetrically in the target tissue, beneath a surface of the healthy tissue. 
     
     
       4. The method of  claim 1 , wherein the bipolar energy delivered during the delivering energy to the body lumen is sufficiently low that differences in tissue properties, including thermal conduction, heat capacity, innate blood perfusion, and distance from well perfused tissue, cause heat to be drawn from the healthy tissue at a rate that avoids significant thermal damage to the healthy tissue, while allowing heat to build up in the target tissue. 
     
     
       5. The method of  claim 4 , wherein the delivering energy to the body lumen heats the target tissue to a temperature sufficient to efficaciously alter the target tissue without causing sufficient thermal damage to the healthy tissue by heating both the healthy tissue and the target tissue so that a temperature of the healthy tissue temperature exceeds a given temperature at which the healthy tissue can dissipate the heat in a steady state such that heat is retained sufficiently to treat the target tissue while avoiding significant thermal damage to the healthy tissue by allowing the tissue properties of the healthy tissue to draw heat away from the healthy tissue. 
     
     
       6. The method of  claim 1 , wherein the delivering energy to the body lumen heats both the healthy tissue and the target tissue so as to cause a difference between a temperature of the healthy tissue and a temperature of the target tissue, the temperature of the healthy tissue being less than the temperature of the target tissue, wherein the difference in temperature is due at least in part to a difference between a thermal time constant of the healthy tissue and a thermal time constant of the target tissue. 
     
     
       7. The method of  claim 1 , wherein the bipolar energy is delivered in the form of pulses. 
     
     
       8. The method of  claim 1 , wherein the delivering energy has an average rate of delivery to the treatment area and the healthy tissue has a rate of energy dissipation, wherein an order of magnitude corresponding to the average rate of delivery is about the same as an order of magnitude corresponding to the rate of energy dissipation of the healthy tissue. 
     
     
       9. The method of  claim 1 , wherein the delivering energy to the body lumen includes heating the target tissue to a temperature between about 50° C. and about 65° C. 
     
     
       10. The method of  claim 1 , wherein the energizing the selected electrode pairs includes energizing each selected electrode pair with between 0.625 and 180 Joules. 
     
     
       11. The method of  claim 10 , wherein the energizing the selected electrode pairs includes energizing each selected electrode pair with between 4 and 15 Joules. 
     
     
       12. The method of  claim 1 , wherein the energizing the selected electrode pairs comprises energizing each selected electrode pair for 0.5 to 180 seconds. 
     
     
       13. The method of  claim 1 , wherein the delivering energy to the body lumen with the plurality of energy delivery zones is done for less than 90 seconds in each of the plurality of energy delivery zones. 
     
     
       14. The method of  claim 1 , wherein the plurality of electrodes are energized with a generator, the method further comprising:
 measuring a characteristic of the target tissue or the healthy tissue with the plurality of electrode pairs energized by the generator, wherein the delivering energy comprises applying a given treatment energy based on the measured characteristic. 
 
     
     
       15. The method of  claim 14 , wherein the characteristic comprises a load impedance of the target or healthy tissue of the body lumen engaged with the plurality of electrodes. 
     
     
       16. The method of  claim 14 , the given treatment energy is within a desired range of voltages or currents applied in response to a measured load impedance being within a preferred range of impedances. 
     
     
       17. The method of  claim 14 , wherein the generator is an RF generator and the energy is RF energy, and wherein the delivery of energy with the plurality of electrodes is controlled with a controller of the RF energy by selectively directing RF energy to multiple electrodes of the plurality of electrode pairs that include electrodes in contact with the healthy tissue. 
     
     
       18. The method of  claim 1 , wherein, x ranges from 0.50 to 2.00 mm. 
     
     
       19. The method of  claim 1 , wherein, x ranges from 0.75 to 1.50 mm. 
     
     
       20. A method of treating a target tissue within a treatment area disposed about a body lumen, comprising:
 providing a catheter having a catheter body and an energy delivery portion mounted on the catheter body, wherein the energy delivery portion comprises a balloon having a plurality of electrodes spaced apart about a circumference of the balloon; 
 inserting the energy delivery portion of the catheter into the body lumen, positioning the energy delivery portion adjacent the treatment area, and expanding the balloon so that the plurality of electrodes radially engage the body lumen and contact between the plurality of electrodes and the body lumen defines a plurality of separate energy delivery zones within the treatment area, wherein the treatment area includes the target tissue and a healthy tissue; 
 delivering energy to the body lumen at the plurality of energy delivery zones, each of which is small compared to the treatment area so that each of the plurality of energy delivery zones are separated about the balloon, wherein delivering energy comprises energizing the plurality of electrodes so as to therapeutically heat the target tissue through the healthy tissue so that the target tissue is heated sufficiently to efficaciously alter the target tissue without causing sufficient thermal damage to the healthy tissue, wherein at least some electrodes of the plurality heat the healthy tissue without therapeutically heating the target tissue, wherein the plurality of electrodes are energized without identifying which of the plurality of electrodes heat the target tissue, wherein the plurality of electrodes are spaced apart around the circumference, wherein the delivering energy further comprises energizing selected electrode pairs of the plurality of electrodes with a bipolar energy, and wherein the bipolar energy is delivered from the selected electrode pairs of the plurality of electrodes according to a formula as follows:
   power= b *x^2* L *( t ^(—0.59))
 
 
 
       where b ranges between 0.2 and 0.6, x is an inner edge-to-edge spacing between electrodes of the selected electrode pairs in millimeters, L is a length of the electrodes of the selected electrode pairs in millimeters, power is in Watts, and t is time of the bipolar energy delivery in seconds. 
     
     
       21. The method of  claim 20  wherein the body lumen comprises an artery and wherein the treatment area extends along a length of an artery. 
     
     
       22. The method of  claim 21 , wherein each of the plurality of energy delivery zones is defined by an electrical energy path between the selected electrode pairs of the plurality of electrodes and wherein delivering energy to the treatment area comprises delivering energy from a plurality of differing electrical energy paths through the healthy tissue from a first differing electrode pair of the selected electrode pairs and subsequently energizing or multiplexing between a second differing electrode pair of the selected electrode pairs. 
     
     
       23. The method of  claim 21 , wherein the treatment area extends circumferentially about the body lumen. 
     
     
       24. The method of  claim 21 , wherein the plurality of energy delivery zones extends partly and circumferentially about the body lumen such that, in combination, the plurality of energy delivery zones extend about the circumference of the body lumen. 
     
     
       25. The method of  claim 20 , wherein, x ranges from 0.50 to 2.00 mm. 
     
     
       26. The method of  claim 20 , wherein, x ranges from 0.75 to 1.50 mm.